British scientists have calculated that the amount of methane produced by farting dinosaurs would have affected the planet's atmosphere - and noticeably warmed the climate.
Using cows' digestive processes as a starting point, a team from Liverpool John Moore's University has worked out that sauropods - the group which includes Brontosaurus - would have produced around 520 million tons of methane annually.
They used a scale that links a cow's mass to its methane output and applied it to larger animals. And, they reckon, a 90-ton dinosaur would have produced thousands of liters a day.
Multiplying this by the estimated total population of dinosaurs during the Mesozoic era, around 150 million years ago, gave them the 520 million ton figure.
Climate change has been put forward as one reason for the dinosaurs' demise, with temperatures at the time believed to have been about 18 degrees F higher than they are today.
The team believes that this could be due to methane levels as high as eight parts per million - of which one or two ppm could have emerged from the rears of flatulent animals.
Today, according to the researchers, global output of methane is around 500 million tons, of which cows produce between 50 and 100 million.
"A simple mathematical model suggests that the microbes living in sauropod dinosaurs may have produced enough methane to have an important effect on the Mesozoic climate, study leader Dr Dave Wilkinson told the Daily Telegraph.
"Indeed, our calculations suggest that these dinosaurs could have produced more methane than all modern sources - both natural and man-made - put together."
The research appears in Current Biology.